Source/JavaScriptCore/b3/air/AirReportUsedRegisters.cpp

/*
 * Copyright (C) 2015-2017 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#include "config.h"
#include "AirReportUsedRegisters.h"

#if ENABLE(B3_JIT)

#include "AirCode.h"
#include "AirInstInlines.h"
#include "AirPadInterference.h"
#include "AirRegLiveness.h"
#include "AirPhaseScope.h"

namespace JSC { namespace B3 { namespace Air {

void reportUsedRegisters(Code& code)
{
    PhaseScope phaseScope(code, "reportUsedRegisters");
    
    static constexpr bool verbose = false;

    padInterference(code);
    
    if (verbose)
        dataLog("Doing reportUsedRegisters on:\n", code);

    RegLiveness liveness(code);

    for (BasicBlock* block : code) {
        if (verbose)
            dataLog("Looking at: ", *block, "\n");
        
        RegLiveness::LocalCalc localCalc(liveness, block);

        for (unsigned instIndex = block->size(); instIndex--;) {
            Inst& inst = block->at(instIndex);
            
            if (verbose)
                dataLog("   Looking at: ", inst, "\n");

            // Kill dead assignments to registers. For simplicity we say that a store is killable if
            // it has only late defs and those late defs are to registers that are dead right now.
            if (!inst.hasNonArgEffects()) {
                bool canDelete = true;
                inst.forEachArg(
                    [&] (Arg& arg, Arg::Role role, Bank, Width) {
                        if (Arg::isEarlyDef(role)) {
                            if (verbose)
                                dataLog("        Cannot delete because of ", arg, "\n");
                            canDelete = false;
                            return;
                        }
                        if (!Arg::isLateDef(role))
                            return;
                        if (!arg.isReg()) {
                            if (verbose)
                                dataLog("        Cannot delete because arg is not reg: ", arg, "\n");
                            canDelete = false;
                            return;
                        }
                        if (localCalc.isLive(arg.reg())) {
                            if (verbose)
                                dataLog("        Cannot delete because arg is live: ", arg, "\n");
                            canDelete = false;
                            return;
                        }
                    });
                if (canDelete)
                    inst = Inst();
            }
            
            if (inst.kind.opcode == Patch) {
                RegisterSet registerSet;
                for (Reg reg : localCalc.live())
                    registerSet.set(reg);
                inst.reportUsedRegisters(registerSet);
            }
            localCalc.execute(instIndex);
        }
        
        block->insts().removeAllMatching(
            [&] (const Inst& inst) -> bool {
                return !inst;
            });
    }

    if (verbose)
        dataLog("After reportUsedRegisters:\n", code);
}

} } } // namespace JSC::B3::Air

#endif // ENABLE(B3_JIT)